Two undescribed mutations that produce G6PD deficiency in Chilean boys are documented. Both occurred in patients with hereditary non-spherocytic haemolytic anaemia. G6PD Santiago was due to an Arg-Pro change at amino acid 198 because of a C transition at nucleotide 593. G6PD Calvo Mackenna was due to a A-G transition at nucleotide 1138 resulting in a substitution of valine for isoleucine at amino acid 380. The studies were carried out in the Scripps Research Institute in La Jolla, California, USA by courtesy of Dr. Ernest Beutler